Aqueous sodium salt metal cleaner and method of using same

Abstract

An alkali metal cleaning composition for cleaning metal and for inhibiting corrosion of metal. The composition is composed of an alkali carbonate salt, a surfactant, and a corrosion inhibitor. A preferred corrosion inhibitor is an alkali metal silicate. Additional metal corrosion inhibitors such as a combination of a triazole compound and an alkali metal borate also can be employed. Such alkali carbonate compositions are readily water soluble and remain in solution over prolonged storage periods.

What is claimed is: 
     
       1. A method for cleaning a metal surface comprising contacting the metal surface with an aqueous alkaline solution for a sufficient amount of time to remove contaminants therefrom, wherein the aqueous alkaline solution comprises from about 0.1 to about 10 wt. % of an alkali metal cleaning composition, wherein the composition comprises a carbonate salt comprising a sodium carbonate salt, or sodium bicarbonate salt; a surfactant; and sodium silicate salt, and the pH of the aqueous solution ranges from about 8.0 to less than 11.0, and wherein said carbonate salt comprises from about 15 to about 30 wt. % of the dry composition and said surfactant comprises from about 5 to about 30 wt. % of the dry composition, and wherein the composition has a phosphate content based on phosphorous of less than 3 wt. % relative to the total weight of the dry composition, said alkali metal cleaning composition being free of acrylic acid polymers having a molecular weight of 100,000 or greater. 
     
     
       2. The method of claim 1, wherein the sodium silicate salt has a SiO 2  :Na 2  O weight ratio of from about 1.4:1 to about 2.9:1. 
     
     
       3. The method of claim 1, said composition further comprising a triazole compound and an alkali metal borate anticorrosion agent. 
     
     
       4. The method of claim 3, wherein the amount of triazole compound and alkali metal borate each range from about 0.5 to about 1.5 wt. % of the composition. 
     
     
       5. The method of claim 4, wherein the weight ratio of triazole compound to alkali metal borate is about 1:1. 
     
     
       6. The method of claim 3, wherein the triazole compound comprises 1,2,3-benzotriazole; 4-phenyl-1,2,3-triazole; 1,2-naphthotriazole; 4-nitrobenzotriazole; 1,2,3-tolytriazole; 4-methyl-1,2,3-triazole; 4-ethyl-1,2,3-triazole; 5-methyl-1,2,3-triazole; 5-ethyl-1,2,3-triazole; 5-propyl-1,2,3-triazole; or 5-butyl-1,2,3-triazole. 
     
     
       7. The method of claim 3, wherein the alkali metal borate comprises sodium tetraborate pentahydrate or sodium tetraborate decahydrate. 
     
     
       8. The method of claim 1, wherein the carbonate salt consists essentially of the sodium carbonate salt, the sodium bicarbonate salt and mixtures thereof. 
     
     
       9. The method of claim 8, wherein, the sodium carbonate salt comprises sodium carbonate, sodium carbonate decahydrate, sodium carbonate heptahydrate, sodium carbonate monohydrate, sodium sesquicarbonate or mixtures thereof. 
     
     
       10. The method of claim 1, wherein the surfactant is a nonionic surfactant. 
     
     
       11. The method of claim 1, wherein the surfactant is an ethoxylated alkyl-thiol having from 7 to 20 carbons and is ethoxylated with 3 to 15 ethylene oxide units. 
     
     
       12. The method of claim 1, wherein the surfactant comprises a nitrogen-containing surfactant. 
     
     
       13. The method of claim 12, wherein the nitrogen-containing surfactant is an N-alkyl pyrrolidone. 
     
     
       14. The method of claim 1, wherein the solution further comprises a hydrotrope.